The present invention relates to an arrangement for in situ determination of the quantity of turbid matter, aerosol and/or dust in a fluid which flows through a space, by measurement of light which is scattered on solid or fluid particles of turbid matter, aerosols and/or dust of the fluid which is located in the space.
Emission tests are performed in many countries for determining the upper limits of harmful matter in exhaust gases. For performing the proper determinations and verifying the performance of the determinations, it is necessary to have available measuring devices which can measure very small quantities of for example dust in an exhaust flue (chimney) with a concentration under 100 microgram per cubic meter.
The known arrangements for conventional measuring processes make conclusions from a transmission reduction about the content of harmful matter. However, they do not produce useful results with a transmission reduction of under 0.1 promill.
Other processes operate in accordance with the in vitro principle. In accordance with this principle a probe is taken from the exhaust flue by a suction mechanism and it is supplied for evaluation to a measuring cell. In this process inhomogeneties in the stream cannot be taken into consideration.
In accordance with further processes a probe is taken from the measuring space and analyzed in a laboratory.